OEM Denso Iridium Spark Plug Life

[thetoyotaman]

Do all factory Toyota spark plugs that were installed at the factory have a letter stamp on the tip?

How long do these Toyota Denso Iridium plugs really last?

 

[kevin2i]

Mine went 185k before changing --- I didn't notice a letter stamp. Starts faster, but I replaced my starter at the same time I replaced the plugs.

 

[donco]

I replaced mine at 106k when doing the timing belt. I didn't notice any significant ablation, and no significant performance improvement with the new ones, which are also Denso Iridiums.

The bigger concern is leaving the plugs in for that long makes them more difficult to remove. Two of my old ones were in so tight I thought I'd strip the threads getting them out, but they came out ok.